There has long been a major need for a root barrier panel that can be molded in a single piece, that has a male connecting element at one edge and a female connecting element at the opposite edge, that can be manufactured economically and practically by injection molding, and that is such that roots may not grow substantially between panels connected by the male-female elements.
In the absence of the ideal panel indicated in the preceding paragraph, companies in the root barrier industry have had to make do with other things. For example, they have relied on joint strips that had to be separately manufactured and subsequently assembled with the panels. This not only generated increased labor and other costs, but gave rise to the likelihood that there would occasionally be missing or lost strips at the job site.
Another thing that has been proposed and used, because of the long-standing inability to achieve the ideal stated in the first paragraph above, is integral extrusions having integral male joint portions and integral female joint portions. However, extrusions have several major drawbacks. For one thing, it is impossible or impractical to generate extrusions having portions extending transversely to the direction of extrusion. An example is ground locks, which are surfaces that extend substantially horizontally whereas the extruded joints extend vertically (when the panel is in the ground). Reference is made to U.S. Pat. No. 5,070,642 for "Tree Root Deflector Installation". To state another example, it is not possible to have top rails on the extruded panels because such rails also extend transversely to the direction of extrusion. Reference is made to U.S. Pat. No. 5,305,549 for "Method and Apparatus for Deflecting Tree Roots, and Combination of the Apparatus with Tree and Static Structure".
Another of the important problems relative to extrusions is that there are limitations relative to the types of synthetic resin that may be employed. It is frequently not possible or practical to use recycled plastic in extrusions, and this is a substantial environmental and economic consideration.